• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.483-486
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• 2001

This Paper the state-of-the art indirect induction heated boiler and induction heated hot air producer using the voltage-fed series resonant high-frequency inverter whice can operate in the frequency range from 20kHz to 50kHz. A specially-designed induction heater composed of laminated stainless assembly with many tiny holes and interconnected spot welding points between stainless plates is inserted into the ceramic type vessel with external working coil connected to the inverter and tubelence fluid through this induction heater in moving fluid generates in the vessel. The operating performances of this unique appliance in next generation and its effectiveness are evaluated and discussed from a practical point of view.

• Proceedings of the Optical Society of Korea Conference
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• 1989.02a
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• pp.65-69
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• 1989

Mather type dense plasma focus device was develooped for the feasibili쇼 study in its application to the x-ray lithography. To etermine the electrical characteristics,the temporal begavior of the discharge current and the voltage was measured by using the Rogowski coil and the high voltage probe respectively. The results are 9 $\mu\textrm{s}$ of the period, 18m$\Omega$ of resistance and 0.16$\mu$Η of inductance. The average current sheath velocity was measured by the light signal emitted at the moving plasma sheath. The light signal was detected through two fiber bundles. When the applied voltage was 13 kV and the initial jpressure of argon was 21.8 Pa, the best plasma focus was occurred. The x-ray emission characteristics from the plasma focus was determined by the x-ray pictures taken by pinhole camera. It is focus that the plasma was focused at 1.4 cm distant position above the center electrode and its diameter was about 1.0 m.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.396-401
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• 2001

Heat transfer analysis of a iron core type linear motor for surface mounting device applications was considered in this study. In order to avoid the complex conjugate problem a fluid flow regime and a solid regime were considered separately. First, film coefficients of the moving parts were evaluated from computational fluid dynamic analysis and those of the stationary parts from the existing empirical or analytic correlations. And then, by applying them, internal and external temperatures of the linear motor pal1s were computed through finite element analysis. Both computation and measurement were carried out with respect to motor driving power. The measurement did not exhibit a linear temperature variation trend with respect to motor power while the computation revealed a linear correlation. Nonetheless, the computations agreed with the measurements within an error range of 20%. It indicates that an adequate heat transfer model for the reciprocative coil assembly may help more exact prediction.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.3
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• pp.240-249
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• 2008

This paper presents an electromagnetic design method for magneto-rheological (MR) valves. Since the apparent viscosity of MR fluids is adjusted by applying magnetic fields, the MR valves can control high-level fluid power without any mechanical moving parts. In order to improve the performances of the MR valve, it is important that the magnetic field is effectively supplied to the MR fluid. For the purpose, the magnetic circuit composed with the yoke for forming magnetic flux path, the electromagnetic coil and the MR fluid should be well designed. In order to improve the static characteristic of the MR valve, the length of the magnetic flux path is decreased by removing the unnecessary bulk of the yoke. Also, in order to improve its dynamic and hysteretic characteristics, the magnetic reluctance of the magnetic circuit should be increased by minimizing the cross-sectional area of the yoke through which the magnetic flux passes. After two MR valves, one is a conventional type valve and the other is the proposed one, are designed and fabricated, their performances are evaluated experimentally.

• The Journal of Engineering Geology
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• v.4 no.2
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• pp.207-218
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• 1994

The natural constants of moving coil type geophone can be determined by free impedance and step force method. The former method was desirable for the measurement of natural frequency($f_o$), inertial mass(m) and damping factor($h_o$), but the latter method for sensitivity(G). In particular, the value by the latter method should be corrected for the noise by the long period movement of measurement device. The results of frequency characteristics from these constants operate the accelerometer and displacement system in the boundary of natural frequency.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1593-1598
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• 1994

Recently rotary-arc, thermal expansion and their composite interrupters are widely used in the distribution power system because they have lots of advantages in making the larger interrupting capacity, the smaller size, the lighter weight and the less surge. A model interrupter of rotary-arc type, which has constant stroke and thermal expansion volume, was studied by varying the design parameters, i.e. the number of turns of the driving coil, the inner diameter of the moving contact, the gas pressure and the shape of the fixed contact for this project. Short cicuit current interrupting tests were conducted to the model interrupters by varying the requirements from 42% to 175% of the test voltage, interrupting current and transient recovery voltage for the test duty No.4 of 7.2kV 12.5kA single phase test. The pressure rise, minimum and maximum arcing times were analyzed for each model interrupter. All types of model interrupters showed good interrupting performances and sufficient design margins for the ratings.

• Journal of the Korean Society for Railway
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• v.19 no.3
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• pp.324-330
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• 2016

A magnetic contactor is a switching device widely used for electric circuits. For the operation of magnetic contactors, magnetic coils are essential; these coils create and interrupt the electric circuit. In this paper, the finite element analysis model was developed to reflect the experimental data, and was verified through alteration of the applied voltages and the numbers of turns. Effects of electromagnetic force on the geometrical variations of the facing poles for fixed and moving cores of two magnet coils were investigated. In addition, effects of slope and air gap size between two facing poles on the electromagnetic force were explored through the distribution of the magnetic flux density in the magnetic coils of a push-type solenoid. Through this analysis, the characteristics of the electromagnetic force against the facing poles were explored.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.10
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• pp.109-115
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• 2016

In this paper, In this paper, we use two methods to compare the slim speakers. That way, the diaphragm scan using laser and diaphragm photographed using a thermal imaging camera. Slim speaker has the structure of a flat plate type. Break-up mode by this characteristic is displayed in a larger size. Further, since the installation space is narrow, it has limited moving coil cooling. As a result, the break-up mode slim speakers, a significant impact on quality. In this study, try to connect the break-up mode of the diaphragm, the heat transfer mode of the diaphragm. Experiment for comparison, a two-step. The first step is to measure the divided vibration through the vibration plate scan. The second step measures the diaphragm photographed using a thermal imaging camera. Then, compare the results of both of the same frequency. Thus, comparing the heat transfer pattern and the pattern of break-up mode. Tend to be analysis of break-up mode from the pattern comparison, and document for the optimum design.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.4
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• pp.333-336
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• 2017

A speaker diaphragm generates a divided vibration. The influence of the break-up mode is sufficient to cause a shape change in the diaphragm. In this paper, is widely used in ultra-thin multi-media devices, including smart phones is the advance guard of the IT sector, the micro-speakers and its target. Micro-speakers are different from general speakers. The plate has structural form and space constraints. In particular, they utilize a closed-type drive space. It is difficult to provide cooling for the auxiliary suspension structure because of the heat generated in the moving coil. The present study considered the relationship between the break-up mode and the heat transfer of the diaphragm. An experiment was conducted in two stages to compare the embodiment of the break-up mode and heat transfer in a certain frequency range. The changes in the heat were determined through measurements and thermal imaging of the break-up mode. The break-up mode tendency of the diaphragm could be rapidly predicted based on the imaging results using the thermal imaging camera. This will help in the optimal design of micro-speakers.